Application of high-resolution ESI and MALDI mass spectrometry to metabolite profiling of small interfering RNA duplex

We investigated the application of a high-resolution Orbitrap mass spectrometer equipped with an electrospray ionization (ESI) source and a matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometer to the metabolite profiling of a model small interfering RNA (siRNA) duplex TSR#34 and compared their functions and capabilities. TSR#34 duplex was incubated in human serum in vitro, and the duplex and its metabolites were then purified by ion exchange chromatography in order to remove the biological matrices. The fraction containing the siRNA duplex and its metabolites was collected and desalted and then subjected to high-performance liquid chromatography (HPLC) equipped with a reversed phase column. The siRNA and its metabolites were separated into single strands by elevated chromatographic temperature and analyzed using the ESI-Orbitrap or the MALDI-TOF mass spectrometer. Using this method, the 5' and/or 3' truncated metabolites of each strand were detected in the human serum samples. The ESI-Orbitrap mass spectrometer enabled differentiation between two possible RNA-based sequences, a monoisotopic molecular mass difference which was less than 2 Da, with an intrinsic mass resolving power. In-source decay (ISD) analysis using a MALDI-TOF mass spectrometer allowed the sequencing of the RNA metabolite with characteristic fragment ions, using 2,4-dihydroxyacetophenone (2,4-DHAP) as a matrix. The ESI-Orbitrap mass spectrometer provided the highest mass accuracy and the benefit of on-line coupling with HPLC for metabolite profiling. Meanwhile, the MALDI-TOF mass spectrometer, in combination with 2,4-DHAP, has the potential for the sequencing of RNA by ISD analysis. The combined use of these methods will be beneficial to characterize the metabolites of therapeutic siRNA compounds. Copyright ? 2012 John Wiley & Sons, Ltd.     

Facile one‐step fabrication of highly transparent and flexible superhydrophobic substrate by room‐temperature ion irradiation method

Highly transparent (transparency 96.5%), flexible and antireflective superhydrophobic (water contact angle >150°) surfaces have been fabricated at room temperature by the ion irradiation method. This one‐step fabrication route was fairly easy to carry out without any heat or chemical treatment and can be completed within few seconds. This novel chemical free fabricating strategy could be extended to numerous polymeric substrates to achieve transparent and flexible superhydrophobic structures for their potential applications in diverse fields. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Polarization Rotation in the Monoclinic Perovskite BiCo(1-x) Fe(x) O(3)

The monoclinic perovskite BiCo(1-x) Fe(x) O(3) (x≈0.7) undergoes a second-order structural transition from tetragonal to monoclinic, which is accompanied by a rotation of the polarization vector from the [001] to [111] directions of a pseudo cubic cell. The crystal structure, determined by electron diffraction and powder synchrotron X-ray diffraction, was the same as that of Pb(Ti(1-x) Zr(x) )O(3) at the morphotropic phase boundary.     

Wide-Range 2D Lattice Correlation Unveiled for Columnarly Assembled Triphenylene Hexacarboxylic Esters

Dipole bridge: Liquid-crystalline (LC) triphenylenes self-assemble columnarly into a hexagonal geometry with a wide-range 2D lattice correlation, for which distal and proximal dipole-dipole interactions are considered responsible. By virtue of the strong intercolumnar interaction, the LC columns of the triphenylene can spontaneously align homeotropically on the 12 different substrates examined (POM=polarized optical microscopy).     

Reactions of o-benzyne with propargyl and benzyl radicals: potential sources of polycyclic aromatic hydrocarbons in combustion

The kinetics and mechanisms of the reactions of o-benzyne with propargyl and benzyl radicals have been investigated computationally. The possible reaction pathways have been explored by quantum chemical calculations at the M06-2X/6-311+G(3df,2p)//B3LYP/6-311G(d,p) level and the mechanisms have been investigated by the Rice-Ramsperger-Kassel-Marcus theory/master-equation calculations. It was found that the o-benzyne associates with the propargyl and benzyl radicals without pronounced barriers and the activated adducts easily isomerize to five-membered ring species. Indenyl radical and fluorene + H were predicted to be dominantly produced by the reactions of o-benzyne with propargyl and benzyl radicals, respectively, with the rate constants close to the high-pressure limits at temperatures below 2000 K. The related reactions on the two potential energy surfaces, namely, the reaction between fulvenallenyl radical and acetylene and the decomposition reactions of indenyl and α-phenylbenzyl radicals were also investigated. The high reactivity of o-benzyne toward the resonance stabilized radicals suggested a potential role of o-benzyne as a precursor of polycyclic aromatic hydrocarbons in combustion.     

Avron–Herbst Type Formula in Crossed Constant Magnetic and Time-Dependent Electric Fields

In this paper, we give an Avron?CHerbst type formula for the propagator generated by the free Hamiltonian with crossed constant magnetic and time-dependent electric fields. As an application of the formula, we give a result of the existence of the wave operators under some appropriate conditions on the time-dependent electric field and the potential. Finally, in the case where the electric field is time-independent, we consider the problem of the asymptotic completeness of the wave operators.     

Reversible photoswitching of the coordination numbers of silicon in organosilicon compounds bearing a 2-(phenylazo)phenyl group

Several organosilicon compounds bearing a 2-(phenylazo)phenyl group were synthesized from the corresponding chlorosilanes and 2-lithioazobenzene prepared by halogen-lithium transmetalation of 2-iodoazobenzene. Their structures were determined by (1)H, (13)C, (19)F, and (29)Si NMR spectra, UV-vis spectra, and X-ray crystallographic analyses. In the UV-vis spectra, silyl groups caused red shifts of both the n-pi and pi-pi transitions of the azo group compared with the transitions of the unsubstituted azobenzene. The E-isomers of the fluorosilanes showed an intramolecular interaction between a nitrogen atom of the azo group and the silicon atom, leading their intermediate structures between a distorted trigonal bipyramidal structure and a tetrahedral structure around the silicon atoms, which were revealed by the X-ray crystallographic analyses and the NMR spectra. On the other hand, silanes without fluorine atoms showed tetrahedral structures in the absence of such an interaction. The photoirradiation of the E-isomers of the fluorosilanes afforded reversibly the corresponding Z-isomers in good yields. The silicon atoms of the Z-isomers were found to be tetracoordinate in the absence of Si-N interactions by the (29)Si NMR spectra. The coordination numbers of the silicon atom of the fluorosilanes were reversibly switched between four and five by photoirradiation. These properties were compared to those of a tetrafluoro[2-(phenylazo)phenyl]silicate.